There have been some cases where a stent is implanted in order to push out the lumen walls and keep them in an expanded state for the purpose of preventing restenosis, by means of a device comprising an outer catheter that holds the stent at the tip and an inner piston that pushes forward the stent after the deployment thereof. The stent, as disclosed in Japanese Patent No. JP-B-4703798 (Patent Document 1) for example, includes multiple tubular divided bodies arranged at given distances from each other in the axial direction, and multiple connection sections by which divided bodies axially adjacent to each other are connected with each other. Furthermore, the tubular divided bodies includes multiple linear sections extending in the axial direction arranged along the circumference at nearly equal intervals, and circumferentially adjacent linear sections are connected with each other by turning portions at the end in the axial direction to make zigzag turns in the axial direction so as to be linked in the circumferential direction.
Meanwhile, since an expanded stent is placed in the lumen for a long time, it is required to be stably retained in the initial form after being expanded. That is, the expanded stent requires enough configurational stability against compressive, tensile and torsional forces in order to prevent irregular deformation such as protrusion of the turning portion due to the action of external forces caused by deformation of lumens such as that of expansion, contraction or twisting. At the same time, the expanded stent needs to possess excellent flexibility in a twisting direction to be able to follow the curving deformation of the lumen while keeping an approximate shape of a circular cylinder.
Since the stent described in Patent Document 1 is arranged with many connection sections at equal intervals that are provided on both sides of each linear section in the axial direction, the stent has enough stiffness to achieve configurational stability against compressive, tensile and torsional forces. However, the stent is likely to be insufficient in flexibility in the twisting direction, as shown in FIG. 15, leading to a likelihood of irregular deformation such as that of bending or crushing at a bent portion in response to bending forces.
One option for enhancing the stent's flexibility in the twisting direction is to decrease the number of connection sections 14 as shown in the stent 300 in FIG. 16, while arranging the connection sections 14 provided on both sides of each tubular divided body 12 to have them linked to linear sections 16 different from each other. However, in such a structure, although the flexibility of the stent is enhanced in the twisting direction, configurational stability tends to be insufficient due to reduced stiffness in the axial direction, which posed a likelihood of irresistibility against compressive forces and the like in the axial direction causing irregular plastic deformation as shown in FIG. 17.